SYNTHESIS AND NONLINEAR-OPTICAL CHARACTERIZATION OF SPIN-COATED FILMSOF TRIBLOCK COPOLYMERS CONTAINING DURHAM POLYACETYLENE

Sequential ring-opening metathesis polymerization of either norbornene or 9-methyltetracyclo-[6.2.1.1(3,6)0(2,7)]dodec-4-ene (MTD) and uorom ethyl)tricyclo[4.2.2.0(2,5)]deca-3,7,9-triene (TCDT) with Mo(CHCMe(3)) (NAr)(OCMe(3))(2) (Ar = 2,6-diisopropylphenyl) followed by linking ter mination with a conjugated dialdehyde results in highly soluble A-B-A triblock copolymers containing a precursor to Durham polyacetylene as the central block. A series of copolymers that contained from 10 to 20 0 equiv of TCDT was synthesized. The precursor copolymers were spin co ated to give submicron thin films. In the case of the copolymers made with norbornene, higher spin speeds resulted in a red shift of the UV/ vis spectra of the final polyacetylene-containing copolymer, indicativ e of longer average conjugation lengths within the film. A red shift w as also observed in the UV/vis spectra of copolymers made with more eq uivalents of TCDT. The nonlinear optical susceptibility chi((3)) of th e copolymers was probed with third harmonic generation and degenerate four-wave mixing. chi((3)) increased with increasing equivalents of TC DT. In all cases, the copolymers made with norbornene had larger chi(( 3)) values than the copolymers made with MTD.